A Troubleshooting
General Guidance
• Do not make modifications to the EVM or change the default settings until AFTER it is verified to be working.
• Register readback requires programming MUXOUT_EN = 1 and MUXOUT_SEL = 1. The GUI will also
prompt to configure this register before attempting any readback operation.
• The POR current of the LMX1204EVM is between 400 mA and 500 mA with the CLKIN source disabled, and
550 mA with the CLKIN source enabled and oscillating.
• The power-down current of the EVM is approximately 10 mA.
If Output Not Seen on CLKOUT
CLKOUT should oscillate after POR once CLKIN is powered and enabled. No EVM programming is required just
to get output from CLKOUT.
• Confirm the EVM is connected to 2.5 V, and draws approximately 400 mA to 500 mA before CLKIN is
applied.
• Confirm the reference input is connected to CLKIN and the reference source is powered and enabled.
• Confirm reference frequency is at least 300 MHz, and input power is at least 0 dBm.
• Confirm enabling CLKIN increases the EVM current to approximately 550 mA.
If Device Features Not Active
The POR defaults for LMX1204 disable the LOGICLK, SYSREF, and other features. Only buffer mode is active
by default. Register settings must be updated to observe these features.
• Confirm the USB cable is connected to the EVM.
• Confirm the connection mode is SPI and the USB2ANY interface is indicated in green on the bottom bar.
• If multiple USB2ANY boards are connected, confirm the correct USB2ANY is connected from
USB
Communications → Interface
pop-up using the identify button.
• Ensure all registers have been loaded (Ctrl+L), and that the device current has changed proportional to the
number of functional blocks enabled in the device.
• If a communication issue with the device is suspected, try toggling the POWERDOWN bit from the
User
Controls
page and observe the EVM current. Note that the first write to R0 after POR will be ignored. If
the EVM current does not drop to about 10 mA after POWERDOWN is set, a communication issue may be
preventing programming, or the IC may be damaged.
If Multiplier Frequency Not Accurate
The multiplier requires several registers to be programmed, and a calibration must be triggered by R0 write
whenever the frequency changes or when the multiplier is first selected.
• Confirm the frequency input and output range for the device is appropriate. The GUI will indicate if
frequencies are out of range by highlighting the input or output box with the range violation.
• Ensure that all registers have been loaded (Ctrl+L). This should also calibrate the multiplier.
• Try toggling the RESET bit on the
User Controls
page before loading all registers again (Ctrl+L).
If Divider Frequency Not Accurate
The main clock output divider is designed with the expectation that the register settings will be loaded only
once after POR. In some cases, the main clock output divider does not always cleanly transition between divide
values if the value is changed after POR. To change the divider value, toggle the RESET bit on the
User
Controls
page and load all registers again (Ctrl+L).
Troubleshooting
SNAU266 – JULY 2021
LMX1204EVM User's Guide
23
Copyright © 2021 Texas Instruments Incorporated
